You might believe that knowing about the manufacturing process is useless but think again. When you need a quality PCB design for your next project, knowing what goes down behind the scenes can be more than helpful.
Concerning yourself with the manufacturing process helps you predict and avoid possible errors. That, in turn, speeds up the production itself. Many steps go into producing a quality PCB, so sit tight, and let’s get right into it.
The PCB Manufacturing Process
Here, we’ll look into the steps that make your board go from a blueprint to the real thing.
The very first step of the entire process is, of course, the design itself. First, you or your designer provide the PCB blueprint to the manufacturer. Of course, you must make sure your design ticks all of the requirement boxes for the kind of PCB you want to make.
The design goes through multiple thorough inspections, first to check for errors and then to ensure it’s good to manufacture. That means that your supplier of choice will also inspect your board before clearing it. Once complete, it’s time for the next step.
If your design passes all inspection, what follows is the printing. Suppliers usually use a plotted printer. This printer will use two different inks to create your board: clear ink and black ink.
Clear ink will show non-conductive areas, while black ink will represent the conductive ones. The same method is used when printing the outer layers of the board. In that case, however, the meanings of the ink colors are in reverse.
3. Printing the Inner Layers
Now comes the printing of the inner layers of your PCB. You need no design for this particular step. In fact, your board’s base is first adorned with a layer of a photo-sensitive film made of photo-reactive chemicals. These chemicals will cause the film to harden once in contact with UV lights.
After that, a computer will scan your board, turning it into an image of what will be your future inner layers. That means the inner layers are the spitting image of the base of your board, only in negative print.
Before etching ensues, the photo-sensitive film will need to harden. That means that UV light will flash across your board.
The etching itself is a three-step process this time around. First, the manufacturers remove the dry film. After that comes the etching process we know from before, the one that removes the excess copper while the tin layer guards the necessary copper we need. At the very end of it all, there will be a chemical removal of tin deposits.
This is where your PCB undergoes its first inspection. During this step, manufacturers test the alignment of all layers. The printed circuit board goes through an AOI (automatic optical inspection) to ensure that all of the circuitry matches what’s on the blueprint. Plus, this way of inspecting is where manufacturers can catch any errors or defects.
An optical punch machine will align all of your layers precisely. After this step, you won’t be able to fix any further mistakes, so everything must be right where it needs to be.
Your PCB is now ready for fusion. Once the layers are aligned, they need to merge into one so the board can finally take shape. That is done through the lamination process. The lamination process combines heat and pressure to unite the layers.
Speaking of layers, manufacturers add even more of them to the mix. We’re talking about additional copper and prepreg (epoxy resin) layers over your board’s surface. A machine controls this process entirely, so you can rest easy knowing that everything will go smoothly.
After the lamination process is complete, the PCB is ready for drilling. Drilling does not happen at random because a lot depends on the precisions of the holes. The holes are there to ensure an electrical connection throughout your board. Drilling also reveals and gives access to other layers.
Since the location of these holes matters so much, manufacturers will use an X-ray machine to find the right spots. This step simply requires higher levels of precision.
8. Plating and Electroless Copper Deposition
Now, the holes receive a thin layer of copper on their walls. That is how the process of plating begins. This process helps bring the layer together even more than before.
What follows is a deep chemical cleaning and baths. Said chemicals will help the thin copper layer coat the PCB, as well as find their way into the board’s holes.
9. Outer Layer Imaging
This process is very similar to the process of inner layer imaging. But, there’s going to be a few differences. In this case, manufacturers perform the imaging process in a sterile room to avoid any contamination. A film of photo-resist is stripped before the outer layer is applied.
Similarly to the inner layer, you need no design. A computer will scan your board and produce an image that will soon be ready for printing. Another big difference between outer and inner layer imaging is that, when it comes to the outer layer, the image is a positive print.
10. Plating and Etching
Now it’s time for another round of both plating and etching. Again, the process is not the same as the first time. What differentiates it? It’s not your entire board that gets another electro-plating of copper, but only the parts that are not already covered. After plating is all done — in the same fashion as the first time around — your circuit board will also receive a layer of tin that will protect the copper layer.
The etching itself is a three-step process this time around. First, the manufacturers remove the blue dry film. After that comes the etching process we know from before, the one that removes the excess copper while the tin layer guards the necessary copper we need. At the very end of it all, there will be a chemical removal of tin deposits.
Before the application of the solder mask, your entire PCB needs a deep clean. That’s because this mask will cover the entire surface of your board, and nobody wants any residue trapped in there. Manufacturers apply epoxy ink to the board, after which they flash a UV light so it can harden. Anything that shouldn’t be on the board requires removal.
The board then undergoes baking to receive a tough finish. That is the step that gives your PCB its standard green color.
12. Surface Finish
At this stage, there’s still a lot of areas lacking copper coverage. That’s what this step does. Basically, your board’s surface receives different finishes that will ensure protection and amplify solderability.
For extra solderability, manufacturers will often plate your board with gold or silver. The types of finishes your board will receive depend solely on your specific demands.
You can consider this the very last step in the PCB manufacturing process. However, this step isn’t unimportant at all. It’s quite the opposite. This is the part where any vital information undergoes printing and becomes a part of the board. That includes things like logos, marks, letters for identification, symbols, etc.
After you’ve written whatever you need and desire on your board, it undergoes one final step. It receives yet another coat that requires curing. That is where you can consider your board complete. However, there’s still a bit more to do before shipping it.
At last, the final product has to go through rigorous testing to ensure it’s functionality. Everything needs to be working as perfectly as possible because there’s no room for errors at this stage.
Manufacturers will perform various tests, such as the flying probe test. If it passes all of the tests, and it should, your PCB is clear for one final inspection done by a team of inspectors. This is mostly a visual inspection in which they’ll assess if your board is really good to go. If it has made it this far, nothing should really go wrong.
There are a lot of steps to the PCB manufacturing process, but they’re all done by a machine, so the possibility of any error occurring is low. Creating a good design is also something that ensures the production goes through smoothly.
The manufacturing process doesn’t always take the same amount of time. It all depends on the kind of PCB you’re making. For example, multi-layered PCBs will take more time because they’re more complex to make.
Either way, having all of this information is vital for a fast and successful PCB production. If you have any questions or need advice, please contact us, and we will be more than willing to assist you.